Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$238.59	6.366%	$253.7786	$253.78	$253.80	$253.80
Purchase #2	$236.64	13.712%	$269.0881	$269.09	$269.10	$269.10
Purchase #3	$147.99	11.397%	$164.8564	$164.86	$164.85	$164.90
Purchase #4	$153.28	7.529%	$164.8205	$164.82	$164.80	$164.80
Purchase #5	$238.58	10.857%	$264.4826	$264.48	$264.50	$264.50
Purchase #6	$20.73	3.193%	$21.3919	$21.39	$21.40	$21.40
Purchase #7	$109.90	4.573%	$114.9257	$114.93	$114.95	$114.90
7 purchase totals =	$1,145.71		$1,253.3438	$1,253.35	$1,253.40	$1,253.40